There is a choir but you just missed the auditions. However, you might be able to audition late if you email the prof. Here's the choir's website.
http://mcmasteruniversitycho ir.ca/ I was in the choir last year and I loved it.
There's also a musical theatre club.
I'm in a choir outside of school as well, called the Bach Elgar Choir. I would definitely recommend it if you'd like more of a challenge.